| Error Code | Meaning | Resolution | | :--- | :--- | :--- | | | Another version of VC++ is already installed. | Uninstall newer versions manually using Microsoft's vcredist_x64 cleanup tool. | | 0x81f40001 | Bootstrapper hash mismatch. | Delete %ProgramData%\Epic\Prereqs\ and re-run. | | 1618 | Another installation is in progress. | Reboot the machine and run the exclusive setup before any other software (like Steam). | | 0x80240017 | Windows Installer service corrupted. | Run sfc /scannow and DISM /Online /Cleanup-Image /RestoreHealth . | The "Exclusive" in Multi-Version UE4 Environments A unique challenge arises when a single machine hosts multiple Unreal Engine versions (e.g., 4.25, 4.26, and 4.27). Each version has its own UE4PrereqSetup_x64.exe in its respective Redist folder.
Here is the good news: The design is intelligent. Running the prerequisites for UE4 4.27 will detect that 4.25’s required libraries are subsets of 4.27’s. It will upgrade components where safe but never downgrade a critical system DLL if a newer engine version already deployed it. ue4 prerequisites x64 setup exclusive
UE4PrereqSetup_x64.exe /quiet /norestart To verify successful deployment across a farm, use: | Error Code | Meaning | Resolution |
HKLM\SOFTWARE\Microsoft\VisualStudio\14.0\VC\Runtimes\x64 Even the exclusive setup can fail. Here is how to resolve advanced issues. | Delete %ProgramData%\Epic\Prereqs\ and re-run